Map 工具类

map 工具类

key 是否存在 

/**
     *
     * key是否存在
     * @param map
     * @param key
     * @param <K>
     * @param <V>
     * @return
     */
    public static <K, V> Boolean isExistsInMapByKey(Map<K, V> map, K key) {
        if (map == null || key == null) {
            return false;
        }
        return map.containsKey(key);
    }


    

 value 是否存在

/**
     * Value 是否存在
     * @param map
     * @param object
     * @param <K>
     * @param <V>
     * @return
     */
    public static <K, V> Boolean isExistsInMapByValue(Map<K, V> map, V object) {
        if (map == null || object == null) {
            return false;
        }
        for (K key : map.keySet()) {
            V value = map.get(key);
            if (value.equals(object)) {
                return true;
            }
        }
        return false;
    }

根据key 排序

import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;

/**
 * @Auther: lizhi
 * @Date: 2018/9/12 20:59
 * @Description: 根据map Key 升序降序排列
 */
public class MapSortUtil{

    public static <K, V> Map<K, V> sortMapAscByKey(Map<K, V> map) {
        if (map == null || map.isEmpty())
            return new TreeMap<>();
        Map<K,V> sortMap = new TreeMap(new MapKeyComparatorAsc());
        sortMap.putAll(map);
        return sortMap;
    }

    public static <K, V> Map<K, V> sortMapDescByKey(Map<K, V> map) {
        if (map == null || map.isEmpty())
            return new TreeMap<>();
        Map<K,V> sortMap = new TreeMap(new MapKeyComparatorDesc());
        sortMap.putAll(map);
        return sortMap;
    }

    static class MapKeyComparatorAsc implements Comparator{
        @Override
        public int compare(Object o1, Object o2) {
            int i = o1.toString().compareTo(o2.toString());
            return i;
        }
    }

    static class MapKeyComparatorDesc implements Comparator{
        @Override
        public int compare(Object o1, Object o2) {
            return o2.toString().compareTo(o1.toString());

        }
    }
}

一些其他方法

https://www.cnblogs.com/avivahe/p/5657070.html [转载]